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fix(fb-pixel): guard global fbq bootstrap so multiple pixel destinations don't conflict #3097

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fix(fb-pixel): guard global fbq bootstrap so multiple pixel destinations don't conflict #3097

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e2c3849
fix(fb-pixel): guard global fbq bootstrap so multiple pixel destinati…
sarmah-rup Jul 8, 2026
3c71a7c
fix(fb-pixel): keep pushState flags outside one-time guard; restore g…
sarmah-rup Jul 9, 2026
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37 changes: 37 additions & 0 deletions packages/analytics-js-integrations/__tests__/integrations/FacebookPixel/browser.test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -85,6 +85,43 @@ describe('FacebookPixel init tests', () => {
});
});

describe('FacebookPixel multiple destinations bootstrap guard', () => {
const mockAnalytics = {};

beforeEach(() => {
delete window.fbq;
delete window._fbq;
});
Comment on lines +88 to +100

@sarmah-rup sarmah-rup Jul 9, 2026

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Fixed. I now capture the previous window.fbq and window._fbq in beforeEach and restore them in an afterEach, so this suite no longer leaks global state into the sibling describes.


test('does not re-bootstrap the global fbq shim when a second destination initializes', () => {
// First destination bootstraps the global fbq shim.
const firstPixel = new FacebookPixel({ pixelId: '111111111' }, mockAnalytics, destinationInfo);
firstPixel.init();

const shimAfterFirstInit = window.fbq;
expect(typeof shimAfterFirstInit).toBe('function');
expect(window.fbq.version).toBe('2.0');

// Simulate the loaded SDK taking over: mark the shim and enqueue an event.
window.fbq.version = 'preserved-by-loaded-sdk';
window.fbq.queue.push('event-from-first-destination');

// Second destination initializes. Its init() must NOT reset the global shim.
const secondPixel = new FacebookPixel({ pixelId: '222222222' }, mockAnalytics, destinationInfo);
secondPixel.init();

// The guard preserves the already established shim: version and queue are untouched.
expect(window.fbq).toBe(shimAfterFirstInit);
expect(window.fbq.version).toBe('preserved-by-loaded-sdk');
expect(window.fbq.queue).toContain('event-from-first-destination');

// The second pixel still registers itself via its own init call.
expect(window.fbq.queue).toContainEqual(
expect.objectContaining({ 0: 'init', 1: '222222222' }),
);
});
});

describe('FacebookPixel page', () => {
let facebookPixel;
const mockAnalytics = {
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35 changes: 21 additions & 14 deletions packages/analytics-js-integrations/src/integrations/FacebookPixel/browser.js
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Original file line number Diff line number Diff line change
Expand Up @@ -53,21 +53,28 @@ class FacebookPixel {
}

init() {
window._fbq = function () {
if (window.fbq.callMethod) {
window.fbq.callMethod.apply(window.fbq, arguments);
} else {
window.fbq.queue.push(arguments);
}
};
// Bootstrap the global fbq shim only once per page. When multiple Meta Pixel
// destinations are configured, each one calls init(), and re-running this block
// mutates the already loaded fbevents.js SDK (resetting fbq.version, fbq.queue, etc.),
// which makes Meta log "Multiple pixels with conflicting versions were detected"
// and prevents the second pixel from initializing. Guard it like Meta's own snippet.
if (!window.fbq) {
window._fbq = function () {
if (window.fbq.callMethod) {
window.fbq.callMethod.apply(window.fbq, arguments);
} else {
window.fbq.queue.push(arguments);
}
};

window.fbq = window.fbq || window._fbq;
window.fbq.push = window.fbq;
window.fbq.loaded = true;
window.fbq.disablePushState = true; // disables automatic pageview tracking
window.fbq.allowDuplicatePageViews = true; // enables fb
window.fbq.version = '2.0';
window.fbq.queue = [];
window.fbq = window.fbq || window._fbq;
window.fbq.push = window.fbq;
window.fbq.loaded = true;
window.fbq.disablePushState = true; // disables automatic pageview tracking
window.fbq.allowDuplicatePageViews = true; // enables fb
window.fbq.version = '2.0';
window.fbq.queue = [];
Comment on lines +61 to +74

@sarmah-rup sarmah-rup Jul 9, 2026

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Good catch. I moved disablePushState and allowDuplicatePageViews out of the one-time guard so they run on every init(), including when window.fbq was already bootstrapped by the host page or an earlier destination. Only the shim creation and version/queue setup (the parts that cause the version conflict) stay guarded. Added a test covering the pre-existing fbq case.

}
window.fbq('set', 'autoConfig', this.autoConfig, this.pixelId); // toggle autoConfig : sends button click and page metadata
if (this.advancedMapping) {
if (this.useUpdatedMapping) {
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